For now, ignore errors from creating klinks. This is racy and you can get
it to trigger in 1/4 of the builds with -j 40 on a 24 processor box. Typical
error is:
ln: machine/include: File exists
*** Failed target: .BEGIN
*** Failed command: rm -f machine && ln -s /p/netbsd/cvsroot/src/sys/arch/vax/include machine
*** Error code 1
Stop.
Another approach to fixing this is to create a lockfile or adding other flags
to ln to change its behavior.